[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] xen/mm.h: add helper function to test-and-clear _PGC_allocated
The _PGC_allocated flag is set on a page when it is assigned to a domain along with an initial reference count of 1. To clear this initial reference count it is necessary to test-and-clear _PGC_allocated and then only drop the reference if the test-and-clear succeeds. This is open- coded in many places. It is also unsafe to test-and-clear _PGC_allocated unless the caller holds an additional reference. This patch adds a helper function, clear_assignment_reference(), to replace all the open-coded test-and-clear/put_page occurrences and incorporates in that an ASSERTion that an additional page reference is held. Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx> --- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx> Cc: Julien Grall <julien.grall@xxxxxxx> Cc: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx> Cc: Jan Beulich <jbeulich@xxxxxxxx> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> Cc: Tim Deegan <tim@xxxxxxx> Cc: Wei Liu <wl@xxxxxxx> Cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx> Cc: Tamas K Lengyel <tamas@xxxxxxxxxxxxx> Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx> --- xen/arch/arm/domain.c | 4 +--- xen/arch/x86/domain.c | 3 +-- xen/arch/x86/hvm/ioreq.c | 11 ++--------- xen/arch/x86/mm.c | 3 +-- xen/arch/x86/mm/mem_sharing.c | 9 +++------ xen/arch/x86/mm/p2m-pod.c | 4 +--- xen/arch/x86/mm/p2m.c | 3 +-- xen/common/grant_table.c | 3 +-- xen/common/memory.c | 5 ++--- xen/common/xenoprof.c | 3 +-- xen/include/xen/mm.h | 11 +++++++++++ 11 files changed, 25 insertions(+), 34 deletions(-) diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c index 4f44d5c742..78700d6f08 100644 --- a/xen/arch/arm/domain.c +++ b/xen/arch/arm/domain.c @@ -926,9 +926,7 @@ static int relinquish_memory(struct domain *d, struct page_list_head *list) */ continue; - if ( test_and_clear_bit(_PGC_allocated, &page->count_info) ) - put_page(page); - + clear_assignment_reference(page); put_page(page); if ( hypercall_preempt_check() ) diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c index 147f96a09e..c8c51d5f76 100644 --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -1939,8 +1939,7 @@ static int relinquish_memory( BUG(); } - if ( test_and_clear_bit(_PGC_allocated, &page->count_info) ) - put_page(page); + clear_assignment_reference(page); /* * Forcibly invalidate top-most, still valid page tables at this point diff --git a/xen/arch/x86/hvm/ioreq.c b/xen/arch/x86/hvm/ioreq.c index 7a80cfb28b..129f9fddbc 100644 --- a/xen/arch/x86/hvm/ioreq.c +++ b/xen/arch/x86/hvm/ioreq.c @@ -398,8 +398,7 @@ static int hvm_alloc_ioreq_mfn(struct hvm_ioreq_server *s, bool buf) return 0; fail: - if ( test_and_clear_bit(_PGC_allocated, &page->count_info) ) - put_page(page); + clear_assignment_reference(page); put_page_and_type(page); return -ENOMEM; @@ -418,13 +417,7 @@ static void hvm_free_ioreq_mfn(struct hvm_ioreq_server *s, bool buf) unmap_domain_page_global(iorp->va); iorp->va = NULL; - /* - * Check whether we need to clear the allocation reference before - * dropping the explicit references taken by get_page_and_type(). - */ - if ( test_and_clear_bit(_PGC_allocated, &page->count_info) ) - put_page(page); - + clear_assignment_reference(page); put_page_and_type(page); } diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c index df2c0130f1..9fe66a6d26 100644 --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -498,8 +498,7 @@ void share_xen_page_with_guest(struct page_info *page, struct domain *d, void free_shared_domheap_page(struct page_info *page) { - if ( test_and_clear_bit(_PGC_allocated, &page->count_info) ) - put_page(page); + clear_assignment_reference(page); if ( !test_and_clear_bit(_PGC_xen_heap, &page->count_info) ) ASSERT_UNREACHABLE(); page->u.inuse.type_info = 0; diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c index f16a3f5324..7a643aed53 100644 --- a/xen/arch/x86/mm/mem_sharing.c +++ b/xen/arch/x86/mm/mem_sharing.c @@ -1000,8 +1000,7 @@ static int share_pages(struct domain *sd, gfn_t sgfn, shr_handle_t sh, mem_sharing_page_unlock(firstpg); /* Free the client page */ - if(test_and_clear_bit(_PGC_allocated, &cpage->count_info)) - put_page(cpage); + clear_assignment_reference(cpage); put_page(cpage); /* We managed to free a domain page. */ @@ -1082,8 +1081,7 @@ int mem_sharing_add_to_physmap(struct domain *sd, unsigned long sgfn, shr_handle ret = -EOVERFLOW; goto err_unlock; } - if ( test_and_clear_bit(_PGC_allocated, &cpage->count_info) ) - put_page(cpage); + clear_assignment_reference(cpage); put_page(cpage); } } @@ -1177,8 +1175,7 @@ int __mem_sharing_unshare_page(struct domain *d, domain_crash(d); return -EOVERFLOW; } - if ( test_and_clear_bit(_PGC_allocated, &page->count_info) ) - put_page(page); + clear_assignment_reference(page); put_page(page); } put_gfn(d, gfn); diff --git a/xen/arch/x86/mm/p2m-pod.c b/xen/arch/x86/mm/p2m-pod.c index 4313863066..2e22764950 100644 --- a/xen/arch/x86/mm/p2m-pod.c +++ b/xen/arch/x86/mm/p2m-pod.c @@ -274,9 +274,7 @@ p2m_pod_set_cache_target(struct p2m_domain *p2m, unsigned long pod_target, int p if ( test_and_clear_bit(_PGT_pinned, &(page+i)->u.inuse.type_info) ) put_page_and_type(page + i); - if ( test_and_clear_bit(_PGC_allocated, &(page+i)->count_info) ) - put_page(page + i); - + clear_assignment_reference(page + i); put_page(page + i); if ( preemptible && pod_target != p2m->pod.count && diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c index 4c9954867c..ce6859d51b 100644 --- a/xen/arch/x86/mm/p2m.c +++ b/xen/arch/x86/mm/p2m.c @@ -1609,8 +1609,7 @@ int p2m_mem_paging_evict(struct domain *d, unsigned long gfn_l) goto out_put; /* Decrement guest domain's ref count of the page */ - if ( test_and_clear_bit(_PGC_allocated, &page->count_info) ) - put_page(page); + clear_assignment_reference(page); /* Remove mapping from p2m table */ ret = p2m_set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_4K, diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c index e6a0f30a4b..5ae85e3dad 100644 --- a/xen/common/grant_table.c +++ b/xen/common/grant_table.c @@ -1707,8 +1707,7 @@ gnttab_unpopulate_status_frames(struct domain *d, struct grant_table *gt) } BUG_ON(page_get_owner(pg) != d); - if ( test_and_clear_bit(_PGC_allocated, &pg->count_info) ) - put_page(pg); + clear_assignment_reference(pg); if ( pg->count_info & ~PGC_xen_heap ) { diff --git a/xen/common/memory.c b/xen/common/memory.c index 03db7bfa9e..ab19a4ca86 100644 --- a/xen/common/memory.c +++ b/xen/common/memory.c @@ -388,9 +388,8 @@ int guest_remove_page(struct domain *d, unsigned long gmfn) * For this purpose (and to match populate_physmap() behavior), the page * is kept allocated. */ - if ( !rc && !is_domain_direct_mapped(d) && - test_and_clear_bit(_PGC_allocated, &page->count_info) ) - put_page(page); + if ( !rc && !is_domain_direct_mapped(d) ) + clear_assignment_reference(page); put_page(page); diff --git a/xen/common/xenoprof.c b/xen/common/xenoprof.c index 8a72e382e6..262d537074 100644 --- a/xen/common/xenoprof.c +++ b/xen/common/xenoprof.c @@ -173,8 +173,7 @@ unshare_xenoprof_page_with_guest(struct xenoprof *x) struct page_info *page = mfn_to_page(mfn_add(mfn, i)); BUG_ON(page_get_owner(page) != current->domain); - if ( test_and_clear_bit(_PGC_allocated, &page->count_info) ) - put_page(page); + clear_assignment_reference(page); } } diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h index a57974ae51..1c36c74b8c 100644 --- a/xen/include/xen/mm.h +++ b/xen/include/xen/mm.h @@ -658,4 +658,15 @@ static inline void share_xen_page_with_privileged_guests( share_xen_page_with_guest(page, dom_xen, flags); } +static inline void clear_assignment_reference(struct page_info *page) +{ + /* + * It is unsafe to clear _PGC_allocated without holding an additional + * reference. + */ + ASSERT((page->count_info & PGC_count_mask) > 1); + if ( test_and_clear_bit(_PGC_allocated, &page->count_info) ) + put_page(page); +} + #endif /* __XEN_MM_H__ */ -- 2.20.1.2.gb21ebb671 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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